Sound recording system



Nov. 26, 1946.

G. P. BRUBAKER 2,411,501

SOUND RECORDING SYS TEM Filed May 16, 1944 INVENTQR Ge r e I? Bra/baker m VATTCRNEYI Patented Nov. 26, 1946 2,4iill,5i

2,411,501 SOUND RECORDING SYSTEM George P.

a corporation of Ohio Application May 16, 1944, Serial No.

(Cl. 179-100. i)

6 Claims.

This invention relates to a sound recording systern, and more particularly to one in which a recording head co-operates with a moving record blank to form a sound track.

In such an arrangement, a source of motion is coupled to the record blank to move it at the desired speed past the recording head.

It is one of the objects of this invention to control the motor driving the record blank in such manner that the motor is deenergized when the sound impulses to be recorded have been discontinued.

It is another object of this invention to ensure that the record blank will order of a few seconds.

This invention possesses many other tages, and has other objects which may be made panying and forming part of the present specification. The form will now be described in detail, illustrating the general principles of the invention; but it is to be understood that this detailed description is not to be taken in a limiting sense, since the scope of this invention is best defined by the appended claims.

Referring to the drawing the single figure is a wiring diagram of a system incorporating the invention.

In this system there is shown a source of electrical impulses, such as microphone I, that is in circuit with a source of direct current energy 2 and the primary coil 3 of a transformer 4.

The electrical impulses are thus transmitted to the secondary coil 5 or the transformer 4.

These electrical impulses, as is well understood,

, is shown in the present that is driven by a motor ID.

Motor I8 is shown in this instance as arranged in circuit with a source of direct current energy, such as the battery H. It may also be shunted by a relatively large condenser l2 that reduces the fluctuations of current through the battery 5 l. controlled by a relay l3 having a back contact l4. When the relay I3 is energized, as illustrated, the motor H] is de-energized. When the relay i3 is de-energized, the back contact I4 completes the motor circuit through battery H and acontrol switch It.

The relay I3 is so controlled that it drops its armature it when the impulses to be recorded Erubaiier, Los Angeles, Calif, assignor to Memovox, Incorporated,

Beverly Hills, Calii,

slon device utilizing a separately h ated cathode l8, a control electrode or grid an anode or plate a screen grid 2!, and a cathode heater 22. This heater 22 is shown as provided with heating current from battery I l.

The output circuit f device 5'! thus includes the anode switch 55, and battery ll.

As is well understood, the amount of current 'errcitted to flow in this circuit depends upon the potential difference between the cathode l8 and the grid 59. In the present instance, when there is substantially no potential difierence between the input electrodes l3 and l relay i 3 is operatively energized, and the motor 5 ii is inactive. When the impulses to be recorded are transmitted through the transformer the current in the output circuit including relay i3 is materially reduced, and the armature drops to close the energizing circuit for the motor Hi. How this reduction is eiiected will now be described.

he secondary coil 5 shown as connected at its opposite terminals to cathode i8 and the grid A relatively large resistance 24 of the order of 20 megohms directly connects the cathode l 8 and the grid 1 While the system is inactive,

cathode l3 and the grid is is zero, since they are through the resist- The tube characteristic is such that, an operative current the motor circuit is directly connected together ance 24. under these circumstances, flows through relay i and therefore ole-energized.

When imondary coil exists across the upper and lower terminais of secondary coil 5. This electromotive orce afi'eots the operation of the thermionic tube ii in a way now to be described.

When the upper terminal of the secondary coil is positive, sumcient potential di erence exists between the cathode it and the grid is to produce a space current between these two electrodes. The battery 1 i is so proportioned that the intensity of the signal impulses imposed upon the input side of the electronic emission device ii is of the same order as the potential difference across the source ii. Furthermore, the potential difference impressed upon the plate 556 is quite low, or of the order of 29 to 30 volts.

e force 3 Accordingly, the grid current flowing between cathode l8 and grid l9 during the positive halfcycle of the signaling impulse is relatively heavy, and the plate current is correspondingly reduced to a value that causes the relay It to drop its armature 56. On the other hand, when the upper terminal of the coil 5 is negative, the negative potential thereby imposed upon the grid 19 stops any flow of output current, and thus de-energization of relay i3 is maintained.

Upon the suspension of the transmission of impulses, an interval must elapse before the potential on grid l9 returns to a value such as to reenergize the relay I3. By appropriate proportioning of condenser 23 and resistor 24, this interval can be chosen to be of the order of several seconds. This corresponds to the period or discharge of the condenser 23 through the resistance 24. Usually an interval of about six seconds is sufficient. When the interval is longer, the system returns to the position shown in the figure.

When, for example, the impulses being transmitted are set up by speaking into the microphone I, any slight hesitation of the person using the system would not result in stopping of the turntable 9.

Similarly, when the microphone circuit is first energized after a relatively long period of inactivity, the first few cycles of the voice currents are capable of causing the relay E3 to be de-energized suiiiciently to drop armature it.

The inventor claims: 7

1. In a recording system utilizing a moving record blank: a recording head; means for imparting motion to the blank; means for transmitting impulses to be recorded to the head; and means for causing said motion imparting means to be active during periods when impulses are being transmitted, comprising an electronic emission device; an output circuit for said device and controlling said means for imparting motion; and an input circuit for the device, said input circuit being subjected to the impulses and so proportioned that existence of said impulses causes reduction of the current in the output circuit.

2. In a recording system utilizing a moving record blank: a recording head; means for imparting motion to the blank; means for transmitting impulses to be recorded to the head; and means for causing said motion imparting means to be active during periods when impulses are being transmitted, comprising an electronic emission device; an output circuit for said device and controlling said means and an input circuit for the device, said input circuit being subjected to the impulses and so proportioned that existence of said impulses causes reduction of the current in the output circuit, and including a capacitance and a resistance through which resistance the capacitance can be charged by aid of the impulses, and through which the capacitance can slowly discharge, to maintain said source of motion operative for limited periods between impulses.

3. In a recording system, a motor adapted to impart motion to a record blank, a recording head for co-operating with said blank, means for transmitting electrical impulses to be recorded to the recording head, an electronic tube having an input side and an output side, as well as electrodes associated with the input side and the outlet side, a circuit connecting the input side to the said means, and a device controlling the operation of the motor and connected to the outfor imparting motion;

4 when operatively energized, causing the motor to be rendered inactive, said circuit including a resistance connecting the electrodes associated with the input side, for causing the flow of output current sufficient operatively to energize said device while no impulses are being transmitted, and a capacitance in the path of the impulses, the flow of current between the electrodes associated with the input side when impulses are transmitted being such that the output current is insufficient operatively to energize said device, and, when the impulses cease, the capacitance discharging through the resistance to maintain said energization of the device below operative value for a limited period.

l. In a system of the character described, an electronic emission device having a cathode, a control electrode, and an anpde, means for transmitting impulses so as to impress an alternating potential difference between the cathode and control electrode, and an output circuit connecting the anode and cathode and including a source of potential difierence so as to impress a potential on the anode whichis positive with respect to the cathode, means operating in the absence of the impulses to maintain the potential difference between the cathode and control electrode at a value to cause the flow of current in the output circuit, the potential impressed upon the anode by said source being such, in relation to the characteristics of the electronic emission device and the intensity of the signaling impulses, that the resultant current iiow in the output circuit is materially reduced while impulses are transmitted.

5. In a recording system utilizing a moving record blank: a recording head; means for imparting motion to the blank; means for transmitting impulses to be recorded to the head; and means for controlling said motion imparting means, including an electronic emission device having a cathode, grid, and anode; an input circuit connecting the cathode and grid and responding to the signaling impulses, said input circuit being so constructed and arranged that, when the grid put side, said device,

becomes positive with respect to the cathode, a heavy grid current flows and reduces the flow of current between the cathode and anode, and, when the grid becomes negative, the flow of current from the cathode is blocked; an output circuit connecting the anode and cathode and including a translating device operative to control the motion imparting means.

6. In a recording system utilizing a moving record blank: a recording head; means for imparting motion to the blank; means for transmitting impulses to be recorded to the head; and means for controlling said motion imparting means, including an electronic emission device having cathode, grid, and anode; an input circuit connecting the cathode and grid and responding to the signaling impulses, said input circuit being so constructed and arranged that, when the grid becomes positive with respect to the cathode, a heavy grid current flows and reduces the flow of current between the cathode and anode, and, when the grid becomes negative, the flow of current from the cathode is blocked, said input circuit also including a capacitance in series with the grid, and a high resistance across the grid and cathode; and an output circuit connecting the anode and cathode and including atranslating device operative to control the motion imparting means. v

GEORGE P. BRUBAKER. 

